Electrometallurgical Techniques for DOE Spent Fuel Treatment Final Report (2000) / Chapter Skim
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4 Waste Streams Produced by the Electrometallurgical Technology Process
4 Waste Streams Produced by the Electrometallurgical Technology Process
Pages 45-60
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From page 45... ...
, through its Office of Civilian Radioactive Waste Management (OCRWM/ RW) , and in conjunction with the development of final waste acceptance criteria to be based on Environmental Protection Agency/Nuclear Regulatory Commission Agency regulations, is currently assessing the viability of permanent disposal of spent nuclear fuel (SNF)
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From page 46... ...
It is within this system context that the comm~ttee has evaluated ANL's progress toward obtaining the necessary DOE-RW acceptance of EMT waste forms, qualifying them for final disposal in a geologic repository in the future. To date, both commercial SNF and vitnfied defense HLW have been subjected to detailed charactenzations of their radionuclide-release performance under expected repository conditions.3 The resulting data have been used to guide isolation strategies.
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From page 47... ...
Benedict, and S.G. Johnson, Waste Form Qualification Strategy for the Metal and Ceramic Waste Forms from Electrometallurgical Treatment of Spent Nuclear Fuel, NT Technical Memorandum No.
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From page 48... ...
Keiser, Waste Acceptance Product Specifications for the Waste Forms from Electrometallurgical Treatment of Spent Nuclear Fuel, NT Technical Memorandum No. 116, Argonne National Laboratory, Argonne, IL, 1999.
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From page 49... ...
. METAL WASTE FORMS Background The MWF may contain up to 4 wt % noble metal fission products and up to 11 wt % uranium.l6 l7 The longterm corrosion behavior of this type of alloy is not known and must therefore be determined in the corrosion tests earned out at Argonne National Laboratory-East (ANL-E)
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From page 50... ...
Research at ANL-E has evaluated alloy metallurgy and alloy properties, including mechanical and thermophysical properties and corrosion behavior.l9 The corrosion resistance of SS-15Zr alloys has been determined using immersion tests, electrochemical tests, and accelerated corrosion tests (vapor hydration, high-temperature immersion, and product consistency tests)
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From page 51... ...
Apparently an adherent Cr-rich oxide layer, which will be examined in more detail by TEM and AES in the post-demonstration period, retarded the corrosion reaction. ANL personnel discussed corrosion testing of SS-15Zr MWF samples at a 1998 meeting, concluding that "SS-Zr waste forms are very resistant to the normal corrosion conditions envisioned at the proposed Yucca Mountain geologic repository."29 The effect of radiation on corrosion behavior has been discussed only briefly in presentations to the committee by ANL personnel.30 Calculations carried out at ANL seem to suggest that radiation levels in the MWF are too low to affect the corrosion resistance.
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From page 52... ...
Recommendation: In the post-demonstration phase ANL personnel should subject a few carefully selected samples to additional evaluation by surface analysis to determine the chemical composition of the corrosion products. Recommendation: ANL personnel should concentrate on a few key samples, expose them at higher temperatures and chloride concentrations, and obtain electrochemical and surface analysis data.
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From page 53... ...
Characterization Tests To support repository qualification of the CWF, ANL developed a protocol and conducted a variety of tests and analyses to provide the following information on the CWF: characterization of the phase distribution; waste form corrosion and radionuclide release rates; dissolution data pertinent to modeling CWF corrosion in total system performance assessment calculations; and development of a method that can be used to monitor product consistency and define working ranges for processing variables. Tests have been earned out on samples prepared at a laboratory scale with surrogate fission products, radioactive materials spiked with plutonium, and CWF produced with fully radioactive electrorefiner salt, from a 50 g to 10 kg scale.
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From page 54... ...
This suggests that the CWF repository performance will be comparable to that of the reference borosilicate glass. PCTs conducted on the CWF produced with salt from treating the 100 39ASTM C1174-98, "Standard Practice for Prediction of the Long Term Behavior of Materials, Including Waste Forms, Used in Engineered Barrier Systems (EBS)
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From page 55... ...
Finding: If the long-term release of radionuclides from the CWF is found to control the dissolution of the inert borosilicate glass matrix, and if there is no change in the long-term dissolution rate of the glass matrix under repository conditions, the dissolution rate release performance of the CWF will be at least comparable to borosilicate glass. Finding: The minor component actinides and rare earths form phases separate from sodalite and glass.
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From page 56... ...
Modeling Performance waste form modeling has been earned out at ANL to predict the environmental impact of the ANL ceramic and metal waste forms on the operation of the proposed repository at Yucca Mountain. A simplified schematic of CWF degradation and radionuclide release is shown in Figure 4.3.
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From page 57... ...
Petri, Waste Form Degradation and Repository Performance Modeling, NT Technical Memorandum No. 117, Argonne National Laboratory, Argonne, IL, 1999.
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From page 58... ...
Finding: The dissolution rate model for the glass matrix of the CWF as developed to date suggests that this material should perform like borosilicate glass, and given the small quantity to be emplaced would have a negligible impact on the overall repository performance. Finding: The success criteria (Chapter 6)
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From page 59... ...
The disposition options for this recovered uranium material are constrained by several DOE programmatic decisions and environmental impact statements.45946947 ANL notes that "the depleted uranium byproduct does not have an identified potential commercial application at this time."48 This is attributable to the fact that the radioisotopic composition of the recovered uranium does not meet the AST standard49 for the fabrication of commercial nuclear fuel. ANL further asserts that absent this commercial fuel fabrication option, "the [ennched, dnver-denved]
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